Vehicle

ABSTRACT

A vehicle includes a vehicle body, a front wheel that is disposed anterior to the vehicle body and that is steerable about a steering axis, and a front fork that supports the front wheel. The vehicle body includes a vehicle body frame and a steering rotation unit that is supported on the vehicle body frame and that rotates about the steering axis. The vehicle includes a variable trail length mechanism. The variable trail length mechanism includes an oscillation shaft that extends in a vehicle width direction to thereby connect the front fork oscillatably with the steering rotation unit. The oscillation shaft is disposed at a position overlapping an axis of the front fork in a vehicle side elevational view.

INCORPORATION BY REFERENCE

The present application claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2016-254458 filed on Dec. 27, 2016. Thecontent of the application is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present invention relates to a vehicle.

BACKGROUND ART

A known vehicle includes a variable trail length mechanism that varies atrail length of a front wheel that is disposed anterior to a vehiclebody and is steerable about a steering axis, in addition to, as thevehicle body, a vehicle body frame and a steering rotation unit that issupported on the vehicle body frame to rotate about a steering axis, anda front wheel support member that supports the front wheel (see, forexample, Patent Document 1). The arrangement disclosed in PatentDocument 1 includes the oscillation unit that is formed into a frameshape to support upper portions of the front forks and that isoscillatably connected with a front end portion of an upper portion ofthe steering rotation unit.

PRIOR ART DOCUMENT Patent Document

[Patent Document 1]

Japanese Patent Laid-open No. 2014-172586

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In the known vehicle, however, the center of oscillation of theoscillation unit is spaced away from the front forks. This increasesinertia weight at the time of changing the trail length by oscillatingthe front forks integrally with the oscillation unit, thus tending torequire a large driving force for changing the trail length.

The present invention has been made in view of the foregoing situationand it is an object of the present invention to enable, in a vehicleincluding a variable trail length mechanism, a trail length to bechanged easily.

Means for Solving the Problem

One aspect of the present invention provides a vehicle including avehicle body (10, 210, 310), a front wheel (2) that is disposed anteriorto the vehicle body (10, 210, 310) and that is steerable about asteering axis (Cs), and a front fork (25L, 25R) that supports the frontwheel (2), the vehicle body (10, 210, 310) including a vehicle bodyframe (11) and a steering rotation unit (13, 313, 413) that is supportedon the vehicle body frame (11) and that rotates about the steering axis(Cs). Further, the vehicle includes: a variable trail length mechanism(30, 330, 430) that varies a trail length (t) of the front wheel (2),the variable trail length mechanism (30, 330, 430) including anoscillation shaft (48, 348, 448) that extends in a vehicle widthdirection to thereby connect the front fork (25L, 25R) oscillatably withthe steering rotation unit (13, 313, 413). Still further, theoscillation shaft (48, 348, 448) is disposed at a position overlappingan axis (25 a) of the front fork (25L, 25R) in a vehicle sideelevational view.

In the aspect of the present invention, preferably, the oscillationshaft (48) is disposed at an upper end portion of the front fork (25L,25R).

In the aspect of the present invention, preferably, the front fork (25L,25R) has a fork cap (25 d) that closes an upper surface of the frontfork (25L, 25R), and the oscillation shaft (48) is disposed in the forkcap (25 d).

In the aspect of the present invention, preferably, the steeringrotation unit (13) includes a steering shaft (32) journaled by a headpipe (17) of the vehicle body frame (11), a top bridge (33) fixed to anupper end portion of the steering shaft (32), and a bottom member (34)fixed to a lower end portion of the steering shaft (32). Further,preferably, the variable trail length mechanism (30) includes a drivesource (42) and a linkage mechanism (47) that connects the front fork(25L, 25R) with the bottom member (34) and that oscillates the frontfork (25L, 25R) through a driving force of the drive source (42), andthe oscillation shaft (48) is supported by the top bridge (33).

In the aspect of the present invention, preferably, the steeringrotation unit (313, 413) includes a steering shaft (32) journaled by ahead pipe (17) of the vehicle body frame (11), a top bridge (333, 433)fixed to an upper end portion of the steering shaft (32), and a bottommember (334, 434) fixed to a lower end portion of the steering shaft(32), and the oscillation shaft (348, 448) is disposed at, in a sideelevational view, a position overlapping the axis (25 a) and closer tothe bottom member (334, 434) than to the top bridge (333, 433).

In the aspect of the present invention, preferably, the vehicle furtherincludes a bottom bridge (349) that connects a left and right pair ofthe front forks (25L, 25R), and the oscillation shaft (348) is disposedin the bottom bridge (349) at a position overlapping the axis (25 a) ina side elevational view.

In the aspect of the present invention, preferably, the front fork (25L,25R) constitutes an electronic control suspension capable of changing anaxial length of the front fork, and the vehicle further includes acontrol apparatus (83) that drives the electronic control suspension soas to minimize a change in a vehicle height corresponding to the changein the vehicle height by an operation of the variable trail lengthmechanism (30, 330, 430).

Effects of the Invention

In the vehicle in accordance with the aspect of the present invention,the vehicle body includes the vehicle body frame and the steeringrotation unit that is supported on the vehicle body frame and rotatesabout the steering axis. The variable trail length mechanism includesthe oscillation shaft that extends in the vehicle width direction tothereby connect the front fork oscillatably with the steering rotationunit. The oscillation shaft is disposed at a position overlapping theaxis of the front fork in a vehicle side elevational view. Through theforegoing arrangement, the front fork oscillates about the oscillationshaft disposed at the position overlapping the axi of the front fork, sothat inertia weight at the time of changing the trail length byoscillating the front fork can be reduced. Thus, the trail length can beeasily changed using the variable trail length mechanism.

In accordance with the aspect of the present invention, the oscillationshaft may be disposed at the upper end portion of the front fork. Thisarrangement enables an effective use of a space at the upper end portionof the front fork in disposing the oscillation shaft compactly. Thearrangement further eliminates the need for allocating a space for thefront fork to oscillate at a position superior to the oscillation shaft,thus offering a high degree of freedom in disposing parts.

In accordance with the aspect of the present invention, the front forkmay have the fork cap that closes the upper surface of the front forkand the oscillation shaft may be disposed in the fork cap. The foregoingarrangement allows the oscillation shaft to be disposed using a simplestructure of the fork cap.

In accordance with the aspect of the present invention, the variabletrail length mechanism may include the drive source and the linkagemechanism that connects the front fork with the bottom member and thatoscillates the front fork through the driving force of the drive source,and the oscillation shaft may be supported by the top bridge. Theforegoing arrangement allows the front fork supported by the oscillationshaft of the top bridge to be oscillated via the linkage mechanismconnected with the bottom member, specifically, the front fork can beoscillated by a compact structure to thereby change the trail length.

In accordance with the aspect of the present invention, the oscillationshaft may be disposed at, in a side elevational view, a positionoverlapping the axis and closer to the bottom member than to the topbridge. This arrangement causes the front fork to oscillate about theoscillation shaft disposed at a position closer to the bottom member, sothat a change in vehicle height when the trail length is changed by thevariable trail length mechanism can be minimized.

In accordance with the aspect of the present invention, the vehicle mayfurther include the bottom bridge that connects a left and right pair ofthe front forks, and the oscillation shaft may be disposed in the bottombridge at a position overlapping the axis in a side elevational view.This arrangement allows the oscillation shaft to be provided using asimple structure including the bottom bridge that enhances stiffness ofthe front forks.

In accordance with the aspect of the present invention, the front forkmay constitute an electronic control suspension capable of changing theaxial length of the front fork and the vehicle may further include thecontrol apparatus that drives the electronic control suspension so as tominimize a change in the vehicle height corresponding to the change inthe vehicle height by an operation of the variable trail lengthmechanism. The foregoing arrangement allows a change in the vehicleheight to be minimized even when the trail length is changed by thevariable trail length mechanism. Alternatively, the vehicle height whilethe vehicle is stationary may be lowered by the electronic controlsuspension to thereby improve a property with which the operator (rider)can put both feet on the ground.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a left side elevational view depicting a vehicle according toa first embodiment of the present invention.

FIG. 2 is a left side elevational view depicting the vehicle in which atrail length is positive.

FIG. 3 is a left side elevational view depicting the vehicle in which atrail length is negative.

FIGS. 4A and 4B are schematic views depicting a relation between asteering direction of a front wheel and a position of a center ofgravity of the vehicle.

FIG. 5 is a front elevational view depicting a front portion of thevehicle as viewed from the front.

FIG. 6 is a left side elevational view depicting the front portion ofthe vehicle in an “ordinary state.”

FIG. 7 is a left side elevational view depicting the front portion ofthe vehicle in a “trail length changed state.”

FIG. 8 is a perspective view depicting the front portion of the vehicleas viewed from the front right direction.

FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 5.

FIG. 10 is a cross-sectional view taken along line X-X in FIG. 5.

FIG. 11 is a block diagram depicting a configuration relating to controlof the vehicle.

FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. 6.

FIG. 13 is a left side elevational view depicting schematically a frontportion of a vehicle according to a second embodiment.

FIG. 14 is a left side elevational view depicting a front portion of avehicle according to a third embodiment.

FIG. 15 is a left side elevational view depicting schematically a frontportion of a vehicle according to a fourth embodiment.

FIG. 16 is a side elevational view depicting a modification of thefourth embodiment.

FIG. 17 is a cross-sectional view taken along line XII-XII in FIG. 6according to a fifth embodiment.

FIG. 18 is a schematic view depicting a variation of shapes of a fittingportion and a fitted portion.

FIG. 19 is a schematic view depicting a variation of shapes of thefitting portion and the fitted portion.

MODES FOR CARRYING OUT THE INVENTION

Specific embodiments to which the present invention is applied will bedescribed below with reference to the accompanying drawings. Throughoutthe descriptions given hereunder, longitudinal, lateral, and verticaldirections are relative to the vehicle body unless otherwise specified.In the drawings, an arrow FR denotes a vehicle forward direction, anarrow UP denotes a vehicle upward direction, and an arrow LH denotes avehicle leftward direction.

First Embodiment

FIG. 1 is a left side elevational view depicting a vehicle according toa first embodiment of the present invention.

This vehicle 1 is a motorcycle that includes a vehicle body 10, a frontwheel 2 disposed anterior to the vehicle body 10, and a rear wheel 3disposed posterior to the vehicle body 10.

The vehicle body 10 includes a vehicle body frame 11, an engine 12, asteering rotation unit 13, a seat 14, and a vehicle body cover 15. Theengine 12 serves as a traveling power unit supported on the vehicle bodyframe 11. The steering rotation unit 13 rotates about a steering axis Csat a front end portion of the vehicle body frame 11. An operator sits inthe seat 14. The vehicle body cover 15 covers, for example, the vehiclebody frame 11. The vehicle 1 is a saddled vehicle in which the operatorstraddles the seat 14. The rear wheel 3 is a drive wheel driven by adriving force of the engine 12. It is noted that a motor for driving thefront wheel 2 may be incorporated in a wheel of the front wheel 2 tomake the front wheel 2 a drive wheel.

The vehicle body frame 11 includes a head pipe 17, a main frame 18, adown frame 19, a pivot frame 20, and a seat frame 21. The head pipe 17is disposed at a front end portion of the vehicle body frame 11 andjournals the steering rotation unit 13. The main frame 18 extendsdownwardly toward the rear from the head pipe 17. The down frame 19extends downwardly from a front portion of the main frame 18. The pivotframe 20 extends downwardly from a rear portion of the main frame 18.The seat frame 21 extends toward the rear from an upper portion of thepivot frame 20.

The head pipe 17 is a tubular member disposed to be inclined rearwardlywith respect to a vertical direction in a side elevational view. As withthe front wheel 2 and the rear wheel 3, the head pipe 17 is disposed ata center in a vehicle width direction (lateral direction) of the vehicle1. The steering axis Cs is aligned with an axis of the head pipe 17.

The vehicle 1 further includes front forks 25L and 25R (front wheelsupport members) and a swing arm 24. The front forks 25L and 25R aresupported by the steering rotation unit 13 and extend downwardly towardthe front. The swing arm 24 extends rearwardly from the pivot frame 20to support the rear wheel 3. The rear wheel 3 is journaled on an axle 3a disposed at a rear end portion of the swing arm 24.

The front forks 25L and 25R are provided in pairs on both lateral sidesof the front wheel 2. The front wheel 2 is journaled on an axle 2 a thatis disposed at lower end portions of the front forks 25L and 25R andthat extends in the vehicle width direction.

The front forks 25L and 25R rotate integrally with the steering rotationunit 13. A steering handlebar 26 to be operated by the operator isdisposed at an upper portion of the steering rotation unit 13 via ahandlebar support member 29 (FIG. 5). Specifically, when the operatorturns the steering handlebar 26, the steering rotation unit 13 rotatesabout the steering axis Cs and the front wheel 2 is steered to the leftor right.

The vehicle body cover 15 includes a front cover 27 and a tank cover 28.The front cover 27 is disposed anterior to the head pipe 17. The tankcover 28 covers a portion between the head pipe 17 and the seat 14.

Basic technical aspects relating to the first embodiment will bedescribed below with reference to FIGS. 2 to 4B.

FIG. 2 is a left side elevational view depicting the vehicle 1 in whicha trail length is positive. FIG. 3 is a left side elevational viewdepicting the vehicle 1 in which the trail length is negative. FIGS. 4Aand 4B are schematic views depicting a relation between a steeringdirection of the front wheel 2 and a position of a center of gravity ofthe vehicle 1. In FIGS. 2 and 3, the position of the center of gravityof the vehicle 1, for example, is depicted in the lower half of therespective figures. In FIGS. 2 to 4B, a direction X indicates a fore-aftdirection of the vehicle 1 and a direction Y indicates a roll direction(axial direction about the axis of the direction X) of the vehicle 1. Itis noted that the vehicle forward direction FR is disposed on thedirection X and the vehicle leftward direction LH is disposed on thedirection Y.

FIGS. 2 and 3 depict a reference position state in which the vehicle 1assumes an erect upright position and a steering angle of the frontwheel 2 is 0(°).

A trail length t is a distance between a ground contact point P0 of thefront wheel 2 and a ground contact point P1 of the steering axis Csunder the reference position state. The trail length t is positive onthe forward side with reference to the ground contact point P0 andnegative on the rearward side with reference to the ground contact pointP0. The ground contact point P0 of the front wheel 2 is disposeddirectly below the axle 2 a. A ground contact point P3 of the rear wheel3 is disposed directly below the axle 3 a.

FIG. 2 depicts that the ground contact point P1 of the steering axis Csis disposed anterior to the ground contact point P0 of the front wheel 2and the trail length t is a positive value. FIG. 3 depicts that theground contact point P1 of the steering axis Cs is disposed posterior tothe ground contact point P0 of the front wheel 2 and the trail length tis a negative value.

When the front forks 25L and 25R are leaned further backward withrespect to the steering axis Cs from the state depicted in FIG. 2, theground contact point PO of the front wheel 2 moves forward, resulting ina negative trail length t as depicted in FIG. 3.

It is here noted that the state in which the trail length t is positiveas depicted in FIG. 2 is referred to as an “ordinary state” and thestate in which the trail length t is negative as depicted in FIG. 3 isreferred to as a “trail length changed state.” Specifically, the “traillength changed state” is a state in which the front forks 25L and 25Rare leaned backward with respect to the vehicle body 10 from the“ordinary state.”

As depicted in FIGS. 2 and 3, under the reference position state, thecenter of gravity CG of the vehicle 1 is disposed at the center in thevehicle width direction of the vehicle 1 and between the front wheel 2and the rear wheel 3.

While the vehicle 1 is traveling, the front wheel 2 rolls to move theground contact point to a steered direction (direction in which thewheel is steered). As a result, force is generated in a directionopposite to the steered direction with respect to the center of gravityCG. Specifically, steering in the direction in which the vehicle bodycollapses generates force in the direction in which the vehicle bodystands upright.

When the vehicle 1 is stationary, in contrast, steering the front wheel2 under the “ordinary state” (steered to the right in FIG. 4A) causesthe center of gravity CG of the vehicle 1 to move in a direction(rightward) identical to the steered direction as depicted in FIG. 4A.Thus, when the vehicle 1 is stationary under the “ordinary state,”steering in the direction in which the vehicle body collapses generatesforce in the direction in which the vehicle body collapses. Thisdirection is opposite to the direction during traveling. Specifically,the direction of force acting on the center of gravity CG generated bysteering is reversed corresponding to a change in vehicle speed. Assuch, a vehicle speed range in which the direction of force acting onthe center of gravity CG is reversed exists under the “ordinary state.”This makes it difficult to control collapse of the vehicle body bysteering, so that achieving control to allow the vehicle 1 to stand onits own by steering can be a difficult task.

As depicted in FIG. 4B, when the front wheel 2 is steered under the“trail length changed state” (steered to the right in FIG. 4B), thecenter of gravity CG of the vehicle 1 moves in a direction opposite(leftward) to the steered direction. Specifically, under the “traillength changed state,” steering the front wheel 2 moves the center ofgravity CG in the direction opposite to the steered direction. As aresult, steering in the direction in which the vehicle body collapsesgenerates force F in a direction in which the vehicle body standsupright. Specifically, under the “trail length changed state,” the forceacting on the center of gravity CG of the vehicle 1 by steering isgenerated in an identical direction at all times whether the vehicle 1is stationary or traveling, so that continuity of control over thecollapse of the vehicle body by steering can be maintained. Thus,controlling to allow the vehicle 1 to stand upright by steering is moreeasily achieved in the “trail length changed state” than in the“ordinary state.”

It is here noted that, in addition to the force F, one possibleconsideration for the control to allow the vehicle 1 to stand upright isforce by a movement of the ground contact point in a roll direction ofthe front wheel 2 as a result of steering of the front wheel 2.

The vehicle 1 includes a variable trail length mechanism 30 that variesthe trail length t of the front wheel 2. The variable trail lengthmechanism 30 is disposed anterior to the head pipe 17. A configurationof the variable trail length mechanism 30 and a surrounding portion ofthe variable trail length mechanism 30 will be described below.

FIG. 5 is a front elevational view depicting a front portion of thevehicle 1 as viewed from the front. FIG. 6 is a left side elevationalview depicting the front portion of the vehicle 1 in the “ordinarystate.” FIG. 7 is a left side elevational view depicting the frontportion of the vehicle 1 in the “trail length changed state.” FIG. 8 isa perspective view depicting the front portion of the vehicle 1 asviewed from the front right direction. FIG. 9 is a cross-sectional viewtaken along line IX-IX in FIG. 5. It is noted that FIGS. 5 to 9 eachdepict a condition in which the vehicle body cover 15 has been removed.In FIGS. 6 and 7, the front fork 25L on the left-hand side is notdepicted. In FIG. 8, the front forks 25L and 25R are not depicted.

Reference is made to FIGS. 5 to 9. The steering rotation unit 13includes a steering shaft 32 (FIG. 9), a top bridge 33, and a bottommember 34. The steering shaft 32 is passed through and journaled by thehead pipe 17. The top bridge 33 is fixed to an upper end portion of thesteering shaft 32 that protrudes upwardly from the head pipe 17. Thebottom member 34 is fixed to a lower end portion of the steering shaft32 that protrudes downwardly from the head pipe 17.

The top bridge 33 is a plate-shaped member extending in the vehiclewidth direction at a portion above the head pipe 17. The bar-shapedsteering handlebar 26 is disposed above the top bridge 33. The steeringshaft 32 has an axis that is aligned with the steering axis Cs. Thesteering shaft 32, the top bridge 33, and the bottom member 34constituting the steering rotation unit 13 integrally rotate about thesteering axis Cs.

A bracket 36 is mounted on the steering rotation unit 13. The bracket 36is disposed between the left and right front forks 25L and 25R and so asto extend vertically along the head pipe 17 at a position anterior tothe head pipe 17. The bracket 36 connects the top bridge 33 with thebottom member 34. Specifically, the bracket 36 has an upper end portionfixed to a lower surface of the top bridge 33 by a bolt 36 a (FIG. 7).Additionally, the bracket 36 has a lower end portion fixed to a frontsurface of the bottom member 34 by a bolt 36 c (FIGS. 6 and 8). Thebracket 36 rotates integrally with the steering rotation unit 13.

The variable trail length mechanism 30 includes an oscillation unit 41,an electric motor 42 (drive source), and a ball screw mechanism 43(screw mechanism). The oscillation unit 41 is connected with thesteering rotation unit 13 so as to be oscillatable in the fore-aftdirection. The electric motor 42 supplies a driving force to drive theoscillation unit 41. The ball screw mechanism 43 translates rotation ofthe electric motor 42 to linear motion to thereby oscillate theoscillation unit 41.

The variable trail length mechanism 30 further includes a speed reducer45, a lock mechanism 46, and a linkage mechanism 47. The speed reducer45 transmits rotation of the electric motor 42 with reduced speed to theball screw mechanism 43. The lock mechanism 46 restricts rotation of theelectric motor 42. The linkage mechanism 47 connects the ball screwmechanism 43 with the oscillation unit 41 and the steering rotation unit13.

The oscillation unit 41 of the variable trail length mechanism 30includes an oscillation shaft 48 and a bottom bridge 49 (bridge member).The oscillation shaft 48 extends in the vehicle width direction andconnects the front forks 25L and 25R oscillatably with the steeringrotation unit 13. The bottom bridge 49, while connecting the left andright front forks 25L and 25R, is connected with the linkage mechanism47.

Additionally, the front forks 25L and 25R are connected with each otherin the vehicle width direction by a connecting member 50 disposedsuperior to the bottom bridge 49.

Under the “ordinary state” depicted in FIG. 6, the front forks 25L and25R are disposed anterior to the head pipe 17 in a posture in which afork axis 25 a (axis) extending axially in each of the front forks 25Land 25R extends substantially in parallel with the steering axis Cs.

The front forks 25L and 25R each include a fixed tube 25 b, a movabletube 25 c (FIG. 1), and a fork cap 25 d. The fixed tube 25 b issupported by the bottom bridge 49. The movable tube 25 c is disposed tobe capable of an axial stroke movement with respect to the fixed tube 25b.

The front forks 25L and 25R are each an electronic control suspensioncapable of automatically changing the length in the direction of thefork axis 25 a. The length of the front forks 25L and 25R is changed by,for example, an actuator 25 g (FIG. 11) disposed in each of the frontforks 25L and 25R. The actuator 25 g changes preload of a suspensionspring disposed in each of the front forks 25L and 25R.

The fixed tube 25 b and the movable tube 25 c house therein thesuspension spring and oil, for example. The fork cap 25 d closes anupper opening of the fixed tube 25 b. Specifically, the fork cap 25 dhas a threaded portion formed in an outer peripheral portion thereof andthe threaded portion threadedly engages with an internal threadedportion formed in an inner peripheral portion at an upper end portion ofthe fixed tube 25 b. This fixes the fork cap 25 d to the upper endportion of the fixed tube 25 b.

The connecting member 50 connects the upper end portions of the left andright fixed tubes 25 b. The bottom bridge 49 connects lower portions ofthe left and right fixed tubes 25 b.

Each fork cap 25 d includes an extended portion 25 e that extendsupwardly above the upper end of the fixed tube 25 b. The extendedportion 25 e has an oscillation shaft connecting hole 25 f formedtherein. The oscillation shaft connecting hole 25 f passes through theextended portion 25 e in the vehicle width direction.

The top bridge 33 of the steering rotation unit 13 includes a tubularoscillation shaft support portion 33 a that extends in the vehicle widthdirection. The oscillation shaft support portion 33 a is disposed at afront end portion extending anteriorly the head pipe 17, of the topbridge 33. The oscillation shaft 48 is passed through the oscillationshaft support portion 33 a to thereby be connected with the top bridge33.

The front forks 25L and 25R are journaled on the oscillation shaft 48under a condition in which the oscillation shaft 48 protruding in thevehicle width direction from the oscillation shaft support portion 33 ahas both end portions passing through the oscillation shaft connectingholes 25 f formed in the fork caps 25 d.

Specifically, the oscillation shaft 48 is disposed, in a sideelevational view of the vehicle 1, on the axis 25 a and aligned with theaxis 25 a.

Specifically, the front forks 25L and 25R are connected with the topbridge 33 via the oscillation shaft 48 disposed at the upper endportions thereof and are oscillatable in the fore-aft direction aboutthe oscillation shaft 48 disposed on the axis 25 a.

The bottom bridge 49 of the oscillation unit 41 includes a tubularoscillation unit-side link connection portion 49 a. The oscillationunit-side link connection portion 49 a extends in the vehicle widthdirection and is disposed at a front end portion at a central portion inthe vehicle width direction of the bottom bridge 49. The linkagemechanism 47 has a front end portion connected with the oscillationunit-side link connection portion 49 a.

When the linkage mechanism 47 operates in the “ordinary state” of FIG.6, the bottom bridge 49 moves forward as depicted in FIG. 7 and thefront forks 25L and 25R oscillate about the oscillation shaft 48. Thelinkage mechanism 47 will be described in detail later.

In accordance with the first embodiment, the front forks 25L and 25R arerotatable with the front wheel 2 about the steering axis Cs and areoscillatable in the fore-aft direction with the front wheel 2 about theoscillation shaft 48.

The ball screw mechanism 43 includes a threaded shaft 51, a nut member52, a housing 53, and a guide member 54. The nut member 52 is disposedon the threaded shaft 51. The housing 53 supports the threaded shaft 51.The guide member 54 is disposed to extend in parallel with the threadedshaft 51.

The housing 53 includes a lower wall portion 53 a, an upper wall portion53 b, and a plurality of columnar connecting portions 53 c. The lowerwall portion 53 a supports a first end portion (lower end portion) ofthe threaded shaft 51. The upper wall portion 53 b supports a second end(upper end) side of the housing 53. The connecting portions 53 cvertically connect a circumferential edge portion of the lower wallportion 53 a with a circumferential edge portion of the upper wallportion 53 b.

The lower wall portion 53 a and the upper wall portion 53 b are eachformed into a plate shape that is orthogonal to the threaded shaft 51.The threaded shaft 51 is rotatably supported via bearings 55, 55disposed at central portions of the lower wall portion 53 a and theupper wall portion 53 b. The connecting portions 53 c extendsubstantially in parallel with the threaded shaft 51.

The guide member 54 is formed into a shaft shape connecting the lowerwall portion 53 a with the upper wall portion 53 b. The guide member 54is disposed posterior to the threaded shaft 51.

The nut member 52 integrally includes a nut portion 52 a and a movingportion 52 b. The nut portion 52 a is disposed on the threaded shaft 51.The moving portion 52 b is disposed on the guide member 54. The movingportion 52 b includes a screw mechanism-side link connection portion 52c that extends to the outside of the housing 53 toward the head pipe 17side in the rear.

The threaded shaft 51 has a second end portion 51 a (FIG. 9) passingthrough the upper wall portion 53 b to extend upwardly. An input gear 51b is disposed at the second end portion 51 a.

The ball screw mechanism 43 is disposed in a position such that thethreaded shaft 51 leans backward relative to the vertical direction in aside elevational view. The threaded shaft 51 leans greatly backward withrespect to the steering axis Cs.

The bracket 36 has a mounting surface 36 b on a front surface thereof.The mounting surface 36 b leans backward with respect to the steeringaxis Cs. The ball screw mechanism 43 is disposed such that a rearsurface portion of an upper portion of the housing 53 abuts on themounting surface 36 b. The ball screw mechanism 43 is fixed to themounting surface 36 b by a bolt 56 that is passed from the rear throughthe mounting surface 36 b.

Support pieces 57, 57 extending anteriorly are attached to left andright lateral surfaces at a lower portion of the bracket 36.

The ball screw mechanism 43 is fixed to the support pieces 57, 57 bybolts 58 that are passed through front end portions of the supportpieces 57, 57 from outsides in the vehicle width direction and fastenedto the connecting portions 53 c.

The ball screw mechanism 43 is fixed to the steering rotation unit 13via the bracket 36 and rotates integrally with the steering rotationunit 13 in the steered direction of the front wheel 2.

The ball screw mechanism 43 is disposed anterior to the steeringrotation unit 13 and, in the front elevational view in FIG. 5, disposedbetween the left and right front forks 25L and 25R. The threaded shaft51 is disposed at the center in the vehicle width direction in thevehicle 1 and extends in the vertical direction, as with the steeringaxis Cs. Additionally, the ball screw mechanism 43 is disposed in thevertical direction between the oscillation shaft 48 and the bottombridge 49.

The linkage mechanism 47 includes a first link 61, a second link 62, anda third link 63. The first link 61 extends anteriorly from the bottommember 34. The second link 62 extends posteriorly from the bottom bridge49 and is connected with a front portion of the first link 61. The thirdlink 63 connects the first link 61 with the moving portion 52 b of theball screw mechanism 43.

More specifically, as depicted in FIG. 8, the first link 61 includes apair of left and right arm portions 61 a, 61 a, a tubular portion 61 b,and a connecting portion 61 c. The arm portions 61 a, 61 a extendanteriorly from left and right lateral surfaces of the bottom member 34.The tubular portion 61 b connects leading end portions of the armportions 61 a, 61 a in the vehicle width direction. The connectingportion 61 c protrudes anteriorly from a central portion of the tubularportion 61 b.

The first link 61 is rotatably mounted on the bottom member 34 via aconnecting shaft 61 d that extends in the vehicle width direction.

As depicted in FIG. 8, the second link 62 includes a pair of left andright arm portions 62 a, 62 a and a cross member 62 b. The arm portions62 a, 62 a extend posteriorly from left and right end portions of theoscillation unit-side link connection portion 49 a of the bottom bridge49 along a portion above the bottom bridge 49. The cross member 62 bconnects the arm portions 62 a, 62 a in the vehicle width direction.

The second link 62 is rotatably mounted on the oscillation unit-sidelink connection portion 49 a via a connecting shaft 62 c that extends inthe vehicle width direction.

The arm portions 62 a, 62 a of the second link 62 have leading endportions overlapping the tubular portion 61 b of the first link 61 fromthe outsides in the vehicle width direction. The arm portions 62 a, 62 aare rotatably mounted with respect to the first link 61 via a connectingshaft 62 d that is passed through the leading end portions and thetubular portion 61 b.

The third link 63 has an upper end portion rotatably mounted withrespect to the screw mechanism-side link connection portion 52 c via aconnecting shaft 63 a that extends in the vehicle width direction. Thethird link 63 further has a lower end portion rotatably mounted withrespect to the connecting portion 61 c of the first link 61 via aconnecting shaft 63 b that extends in the vehicle width direction.

FIG. 10 is a cross-sectional view taken along line X-X in FIG. 5.

Reference is made to FIGS. 5 to 10. The speed reducer 45 includes abox-shaped speed reducer case 65, first transmission shaft 66, and asecond transmission shaft 67. The first transmission shaft 66 and thesecond transmission shaft 67 are supported by, and housed in, the speedreducer case 65.

The speed reducer 45 is mounted on an upper surface of the ball screwmechanism 43. More specifically, the speed reducer case 65 has a lowersurface portion fixed to the upper wall portion 53 b of the ball screwmechanism 43. Specifically, the speed reducer 45 is supported by thebracket 36 via the ball screw mechanism 43.

In a side elevational view as in, for example, FIG. 6, the speed reducercase 65 extends upwardly toward the front along the upper wall portion53 b.

The speed reducer case 65 includes a screw mechanism-side case portion65 a and a motor-side case portion 65 b integrated with each other. Thescrew mechanism-side case portion 65 a is fixed to the upper surface ofthe ball screw mechanism 43. The motor-side case portion 65 b extendsanteriorly and outwardly in the vehicle width direction from the screwmechanism-side case portion 65 a.

The first transmission shaft 66 is in mesh with the second transmissionshaft 67. The first transmission shaft 66 and the second transmissionshaft 67 are disposed in parallel with the threaded shaft 51 of the ballscrew mechanism 43 and thus lean backward. The second transmission shaft67 meshes with the input gear 51 b disposed at the second end portion 51a of the threaded shaft 51 of the ball screw mechanism 43. The secondend portion 51 a and the input gear 51 b are housed in the screwmechanism-side case portion 65 a.

The electric motor 42 is mounted on the speed reducer 45 via a couplingunit 70 as a joint.

The coupling unit 70 includes a tubular case 71, a drive-side couplingmember 72, and a driven-side coupling member 73. The drive-side couplingmember 72 and the driven-side coupling member 73 are housed in the case71.

The case 71 has an upper end fixed to a lower surface of the motor-sidecase portion 65 b and extends substantially in parallel with thethreaded shaft 51.

The electric motor 42 includes a motor main unit 42 a and a rotary shaft42 b. The motor main unit 42 a houses, for example, a rotor. The rotaryshaft 42 b assumes an output shaft of the electric motor 42. Theelectric motor 42 is formed into a columnar shape that is long in adirection of an axis 42 c of the rotary shaft 42 b.

The electric motor 42 is disposed such that the rotary shaft 42 b can beinserted from below into the case 71 and the motor main unit 42 a isfixed to a lower end of the case 71. Specifically, the electric motor 42is mounted on the steering rotation unit 13 of the vehicle body 10 viathe coupling unit 70, the speed reducer case 65, the ball screwmechanism 43, and the bracket 36.

Under a condition in which the electric motor 42 is fixed to the case71, the axis 42 c of the rotary shaft 42 b extends in parallel with thethreaded shaft 51 of the ball screw mechanism 43. Additionally, the axis42 c is oriented in the vertical direction of the vehicle 1 in a posturein which the axis 42 c leans backward more than the steering axis Csdoes with respect to the vertical direction in a side elevational viewof FIG. 6 and the like.

The electric motor 42, because being disposed so as to be suspendeddownwardly from the motor-side case portion 65 b, is disposed at aposition anterior to the ball screw mechanism 43 and offset laterallyfrom the ball screw mechanism 43. Additionally, the electric motor 42 isdisposed between the left and right front forks 25L and 25R in the frontelevational view in FIG. 5.

The drive-side coupling member 72 and the driven-side coupling member 73connect the rotary shaft 42 b of the electric motor 42 with an inputshaft 75 (FIG. 10) housed in the motor-side case portion 65 b of thespeed reducer 45.

The input shaft 75 is disposed coaxially with the axis 42 c of therotary shaft 42 b of the electric motor 42 and extends in parallel withthe rotary shaft 42 b and the threaded shaft 51.

The input shaft 75 meshes with the first transmission shaft 66 of thespeed reducer 45. The input shaft 75 has an upper end portion supportedby an upper surface portion 76 of the motor-side case portion 65 b via abearing and has a lower end portion supported by a lower surface portion77 of the motor-side case portion 65 b via a bearing.

The lower end of the input shaft 75 protrudes inferiorly the motor-sidecase portion 65 b and is connected with the driven-side coupling member73.

The rotary shaft 42 b of the electric motor 42 has an upper end portionconnected with the drive-side coupling member 72. The drive-sidecoupling member 72 is connected with the driven-side coupling member 73.

The lock mechanism 46 is an electromagnetic clutch disposed coaxiallywith the axis 42 c of the rotary shaft 42 b.

The input shaft 75 includes at its upper end a lock portion 75 a (FIG.10) disposed superior to the upper surface portion 76 of the motor-sidecase portion 65 b. The lock mechanism 46 is mounted from above on theupper surface portion 76 of the motor-side case portion 65 b.

When an electromagnet is not energized, an actuating portion of the lockmechanism 46 is urged by an urging member and engages with the lockportion 75 a of the input shaft 75 and rotation of the input shaft 75 isrestricted. When the electromagnet is energized, the actuating portionof the lock mechanism 46 resists the urging member with a magnetic forceof the electromagnet to be disengaged from the lock portion 75 a of theinput shaft 75.

Specifically, when the lock mechanism 46 is not energized, the inputshaft 75 is unable to rotate and thus the electric motor 42 is unable torotate. When the lock mechanism 46 is energized, the input shaft 75 isable to rotate and thus the electric motor 42 is able to rotate.

The vehicle 1 further includes an automatic steering mechanism 31 thatdrives the steering rotation unit 13 to thereby turn the front wheel 2.

The automatic steering mechanism 31 includes a steering motor 80 and asteering link 81. The steering motor 80 assumes a steering drive source.The steering link 81 serves as a driving force transmission member thattransmits a driving force of the steering motor 80 to the steeringrotation unit 13.

The steering motor 80 is supported on the main frame 18 at a positionposterior to the head pipe 17.

The steering link 81 extends from an output shaft 80 a of the steeringmotor 80 toward the front laterally along the head pipe 17 and isconnected with the top bridge 33 of the steering rotation unit 13.

FIG. 11 is a block diagram depicting a configuration relating to controlof the vehicle 1.

The vehicle 1 includes a control apparatus 83 that performs controlprocesses for operations of the steering motor 80, the electric motor 42and the lock mechanism 46 of the variable trail length mechanism 30, theactuator 25 g of the front forks 25L and 25R, and the engine 12.

In addition, the vehicle 1 includes, as sensors for detecting varioustypes of state quantities required for the control processes performedby the control apparatus 83, a vehicle body inclination sensor 84, asteering angle sensor 85, a trail length sensor 86, a vehicle speedsensor 87, an accelerator operation amount sensor 88, and a fork lengthsensor 89. The vehicle body inclination sensor 84 detects an inclinationangle of the vehicle body 10 in the roll direction. The steering anglesensor 85 detects a steering angle of the front wheel 2 about thesteering axis Cs. The trail length sensor 86 detects the trail length t.The vehicle speed sensor 87 detects a traveling speed of the vehicle 1.The accelerator operation amount sensor 88 detects an operation amountof an accelerator grip on the steering handlebar 26. The fork lengthsensor 89 detects an axial length of each of the front forks 25L and25R.

The control apparatus 83 is an electronic circuit unit including acentral processing unit (CPU), a random-access memory (RAM), a read-onlymemory (ROM), and an interface circuit. The control apparatus 83 ismounted on the vehicle 1. Each of the foregoing sensors 84 to 89 isconnected with the control apparatus 83 and an output (detection signal)of each of the foregoing sensors 84 to 89 is applied to the controlapparatus 83.

The control apparatus 83 drives the engine 12 on the basis of the outputfrom the accelerator operation amount sensor 88, thereby causing thevehicle 1 to travel.

When the electric motor 42 is driven by the control apparatus 83, thevariable trail length mechanism 30 operates to vary the trail length t.

More specifically, rotation of the electric motor 42 is transmitted tothe threaded shaft 51 of the ball screw mechanism 43 via, in sequencefrom the electric motor 42 side, the rotary shaft 42 b, the drive-sidecoupling member 72 and the driven-side coupling member 73, the inputshaft 75, the first transmission shaft 66 and the second transmissionshaft 67 of the speed reducer 45, and the input gear 51 b.

The rotation of the electric motor 42 is transmitted to the threadedshaft 51 with speed greatly reduced by the speed reducer 45.

When the threaded shaft 51 is rotated by the electric motor 42, the nutmember 52 moves linearly on the threaded shaft 51 along the guide member54.

The movement of the nut member 52 on the threaded shaft 51 deforms thelinkage mechanism 47 and, as the linkage mechanism 47 deforms, thebottom bridge 49 that is connected with the second link 62 moves to thefront and rear.

The movement of the bottom bridge 49 in the fore-aft direction causesthe front forks 25L and 25R to oscillate to the front and rear about theoscillation shaft 48, thus changing the trail length t.

In the “ordinary state” depicted in FIG. 6, the nut member 52 is movedby the drive of the electric motor 42 upwardly until the nut member 52abuts on the upper wall portion 53 b. This raises the connecting shaft62 d of the second link 62 and moves the connecting shaft 62 c at thefront end of the second link 62 to the rear, so that the front forks 25Land 25R oscillate toward the rear via the bottom bridge 49. In the“ordinary state,” the trail length t is changed such that the frontwheel 2 is disposed at a rearmost position.

In addition, in the “ordinary state,” the rear surface of the bottombridge 49 abuts on the front surface of the bottom member 34. Thisrestricts a rearward oscillation position of the front forks 25L and25R.

Additionally, in the “ordinary state,” the control apparatus 83 does notenergize the lock mechanism 46 and rotation of the electric motor 42 islocked and restricted by the lock mechanism 46. The lock mechanism 46further restricts movement of the nut member 52, so that the lockmechanism 46 restricts oscillation of the front forks 25L and 25R. Thisprevents the front forks 25L and 25R from changing into the “traillength changed state” from the “ordinary state” as caused by, forexample, an external force from a road surface.

When rotation is transmitted from the ball screw mechanism 43 side tothe electric motor 42 side via the speed reducer 45, the rotation buildsup speed and torque on the ball screw mechanism 43 side is reduced bythe speed reducer 45 and transmitted to the input shaft 75.

In the first embodiment, the lock mechanism 46 is disposed on the inputshaft 75, upstream of the first transmission shaft 66 of the speedreducer 45 in the transmission path of the rotation of the electricmotor 42. This arrangement makes small the torque transmitted from theball screw mechanism 43 to the input shaft 75 even when the nut member52 moves downwardly from the “ordinary state.” Thus, even with the lockmechanism 46 having a smaller locking capacity, the lock mechanism 46can still restricts oscillation of the front forks 25L and 25R.

In the “trail length changed state” depicted in FIG. 7, the nut member52 is moved by the drive of the electric motor 42 downwardly until thenut member 52 abuts on the lower wall portion 53 a. This lowers theconnecting shaft 62 d of the second link 62 and moves the connectingshaft 62 c at the front end of the second link 62 to the front, so thatthe front forks 25L and 25R oscillate toward the front via the bottombridge 49.

Additionally, in the “trail length changed state,” the control apparatus83 does not energize the lock mechanism 46 and rotation of the electricmotor 42 is locked and restricted by the lock mechanism 46. The lockmechanism 46 further restricts movement of the nut member 52, so thatthe lock mechanism 46 restricts oscillation of the front forks 25L and25R. This prevents the front forks 25L and 25R from changing into the“ordinary state” from the “trail length changed state” as caused by, forexample, an external force from the road surface.

In the first embodiment, the electric motor 42 is supported by thesteering rotation unit 13 of the vehicle body 10 via the speed reducer45, the ball screw mechanism 43, and the bracket 36. The electric motor42 can thus be disposed close to the steering axis Cs. The arrangementallows steering inertia of the steering rotation unit 13 to be reduced,so that the front wheel 2 can be easily steered.

The front forks 25L and 25R oscillate about the oscillation shaft 48that is disposed at a position overlapping the fork axis 25 a in a sideelevational view, so that inertia weight developing when the front forks25L and 25R oscillate can be reduced. Thus, the front forks 25L and 25Rcan be oscillated by a small driving force. Additionally, the frontforks 25L and 25R can be oscillated quickly and a change in the traillength t can be made swiftly.

Exemplary operations of the variable trail length mechanism 30, theautomatic steering mechanism 31, and the front forks 25L and 25R will bedescribed below.

When the vehicle speed detected by the vehicle speed sensor 87 exceeds apredetermined speed (e.g., 4 km/h), the control apparatus 83 maintainsthe vehicle 1 in the “ordinary state.” During traveling in the “ordinarystate,” the control apparatus 83 does not energize the lock mechanism 46and oscillation of the front forks 25L and 25R is locked. In the“ordinary state,” the control apparatus 83 reduces a control amount ofthe steering motor 80 of the automatic steering mechanism 31. Thus, inthe “ordinary state,” the operator steers the front wheel 2 via thesteering handlebar 26.

When the vehicle speed detected by the vehicle speed sensor 87 is equalto or lower than, a predetermined speed (e.g., 3 km/h) including astationary state (0 km/h), the control apparatus 83 changes the state ofthe vehicle 1 to the “trail length changed state.”

First, the control apparatus 83 energizes, in the “ordinary state,” thelock mechanism 46 to thereby cancel the oscillation locked state of thefront forks 25L and 25R. The control apparatus 83 next drives theelectric motor 42 to thereby cause the front forks 25L and 25R tooscillate to the front about the oscillation shaft 48 to set the “traillength changed state” and de-energizes the lock mechanism 46 to therebyrestrict oscillation of the front forks 25L and 25R.

When in the “trail length changed state,” the control apparatus 83increases the control amount of the steering motor 80 to steer the frontwheel 2. More specifically, the control apparatus 83 drives the steeringmotor 80 on the basis of outputs from the vehicle body inclinationsensor 84 and the steering angle sensor 85 so that the vehicle 1 standsin an upright position, specifically, inclination based on the vehiclebody inclination sensor 84 is zero. As described previously, in the“trail length changed state,” steering the front wheel 2 moves thecenter of gravity CG in a direction opposite to the steered direction,thus generating the force F (FIG. 4B) that acts in a direction in whichthe vehicle 1 stands upright on its own. Thus, driving the steeringmotor 80 in a direction in which the vehicle body is steered to collapseallows the vehicle 1 to stand upright on its own.

In the “trail length changed state,” the control by the controlapparatus 83 allows the vehicle 1 to stand upright on its own, so thateven when the vehicle 1 is stationary, the vehicle 1 can stand uprighton its own without any support by a stand or the operator.

In the “trail length changed state” and the “ordinary state,” thecontrol apparatus 83 drives the actuator 25 g of the front forks 25L and25R on the basis of the output from the fork length sensor 89 andadjusts the axial length of the front forks 25L and 25R so as tominimize variations in a vehicle height.

More specifically, when the state is changed from the “ordinary state”to the “trail length changed state,” the front forks 25L and 25R leanfurther backward, resulting in a lower vehicle height of the vehicle 1.Thus, the control apparatus 83 drives the actuator 25 g to therebyextend the overall length of the front forks 25L and 25R so that avehicle height identical to a vehicle height in the “ordinary state” canbe obtained even in the “trail length changed state.” This arrangementminimizes changes in maneuverability of the vehicle 1 caused by changesin the trail length t.

The vehicle 1 further includes a steering handlebar rotation mechanismthat makes the steering handlebar 26 capable of relative rotation aboutthe steering axis Cs with respect to the steering rotation unit 13. Thesteering handlebar rotation mechanism is disposed on the upper surfaceof the top bridge 33. The steering handlebar rotation mechanism includesa handlebar rotation motor 543 (see, for example, FIG. 10) that rotatesthe steering handlebar 26 about the steering axis Cs. The handlebarrotation motor 543 is disposed superior to the steering motor 80.

When steering the front wheel 2 using the automatic steering mechanism31, the control apparatus 83 drives the handlebar rotation motor 543 tothereby rotate the steering handlebar 26 with respect to the steeringrotation unit 13. While the vehicle 1 is traveling at low speeds, forexample, the control apparatus 83 causes the steering handlebar 26 torotate through an angle identical to the steering angle of the frontwheel 2 in a direction opposite to the steered direction of the frontwheel 2 by the automatic steering mechanism 31. This approach allowsonly the front wheel 2 to be steered under a condition in which thesteering handlebar 26 is seemed to remain stationary. Thus, even whenthe front wheel 2 is steered by the automatic steering mechanism 31, themovement of the steering handlebar 26 can be prevented from beingimparted to the operator.

The variable trail length mechanism 30 is arranged to make the frontforks 25L and 25R oscillatable and thus includes movable portions. Thevariable trail length mechanism 30 thus can affect stiffness of astructure surrounding the front wheel 2. The inventors clarified throughexperiments and calculations, for example, capability of enhancingmaneuverability of the vehicle 1 in the configuration including thevariable trail length mechanism 30 by increasing stiffness in thevehicle width direction of the front wheel 2 surrounding structure, inparticular.

The following describes, with reference to FIG. 12, for example, astructure that improves stiffness of the front wheel 2 surroundingstructure.

FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. 6.

Reference is made to FIGS. 6, 7, 9, 10, and 12. The bottom bridge 49 ofthe oscillation unit 41 includes a fitting portion 100 that fits in afitted portion 90 disposed on the bottom member 34 of the steeringrotation unit 13. The fitting portion 100 and the fitted portion 90constitute a torsion reduction portion 102 that reduces torsion of theoscillation unit 41 in the vehicle width direction through theoscillation unit 41 combined with the steering rotation unit 13.

The fitting portion 100 is a protrusion that protrudes to the rear froma rear surface 49 b of the bottom bridge 49.

The fitted portion 90 is a recess formed in a front surface 34 a of thebottom member 34. The fitted portion 90 is recessed toward the rear soas to allow the fitting portion 100 to be fitted therein. The fittedportion 90 and the fitting portion 100 are disposed at a center in thevehicle width direction as with the steering axis Cs.

The fitting portion 100 is a triangular protrusion having a leading end100 d protruding to the rear. More specifically, as depicted in FIGS. 7and 12, the fitting portion 100 has a protrusion upper surface 100 a anda protrusion lower surface 100 b that protrude to the rear from the rearsurface 49 b and left and right protrusion lateral surfaces 100 c, 100 c(lateral wall portions) that extend to the rear from the rear surface 49b.

The protrusion upper surface 100 a and the protrusion lower surface 100b extend in a direction orthogonal to the fork axis 25 a in parallelwith each other.

The left and right protrusion lateral surfaces 100 c, 100 c togetherform the fitting portion 100 inclined to have the tapering leading end100 d. The protrusion lateral surfaces 100 c, 100 c assume outer lateralsurfaces in the vehicle width direction of the fitting portion 100.

The fitted portion 90 is a triangular recess formed to taper toward abottom portion 90 d thereof. More specifically, as depicted in FIGS. 7and 12, the fitted portion 90 includes a recess upper surface 90 a, arecess lower surface 90 b, and left and right recess lateral surfaces 90c, 90 c.

The recess upper surface 90 a and the recess lower surface 90 b areformed to extend in parallel with each other. The left and right recesslateral surfaces 90 c, 90 c together form the fitted portion 90 inclinedto have the tapering toward the bottom portion 90 d.

Under the “trail length changed state” depicted in FIG. 7, the bottombridge 49 is spaced away from the bottom member 34 and the fittingportion 100 does not fit in the fitted portion 90.

Under the “ordinary state” depicted in FIGS. 6, 9, 10 and 12, the rearsurface 49 b of the bottom bridge 49 abuts on, and is received by, thefront surface 34 a of the bottom member 34 and the fitting portion 100fits in the fitted portion 90.

Under the “ordinary state,” the protrusion lateral surfaces 100 c, 100 cof the fitting portion 100 abut on the recess lateral surfaces 90 c, 90c of the fitted portion 90 in the vehicle width direction, so that thebottom bridge 49 is rigidly positioned with respect to the bottom member34 in the vehicle width direction. This enhances stiffness of the frontwheel 2 surrounding structure including, for example, the front wheel 2,the front forks 25L and 25R, and the bottom bridge 49, so thatmaneuverability of the vehicle 1 under the “ordinary state” can beimproved.

Additionally, under the “ordinary state,” the protrusion upper surface100 a of the fitting portion 100 abuts on the recess upper surface 90 aand the protrusion lower surface 100 b abuts on the recess lower surface90 b. This rigidly positions the bottom bridge 49 with respect to thebottom member 34 in the vertical direction, so that stiffness of thefront wheel 2 surrounding structure can be enhanced and maneuverabilityof the vehicle 1 under the “ordinary state” can be improved.

The vehicle 1 is set into the “ordinary state” at a speed range higherthan a speed range in the “trail length changed state.” Thus, in thefirst embodiment, stiffness can be effectively improved under the“ordinary state” in which higher stiffness is required than in the“trail length changed state.”

Additionally, because of the protrusion lateral surfaces 100 c, 100 c,the fitting portion 100 tapers toward the leading end 100 d. The fittingportion 100 can thus be easily fitted into the fitted portion 90 so asto be guided along the protrusion lateral surfaces 100 c, 100 c.

It is noted that the fitting portion 100 is required to be configuredsuch that at least the protrusion lateral surfaces 100 c, 100 c abut onthe recess lateral surfaces 90 c, 90 c. For example, under a conditionin which the fitting portion 100 is fitted in the fitted portion 90, theprotrusion upper surface 100 a and the protrusion lower surface 100 bmay be configured to be spaced away from the recess upper surface 90 aand the recess lower surface 90 b, respectively, and thus the fittingportion 100 is configured not to be positioned vertically. Thisalternative configuration enables the fitting portion 100 to be easilyfitted in the fitted portion 90 and dimensional accuracy of the fittingportion 100 and the fitted portion 90 to be easily managed.

Additionally, under the condition in which the fitting portion 100 isfitted in the fitted portion 90, the leading end 100 d of the fittingportion 100 may be configured to be spaced away from the bottom portion90 d of the fitted portion 90. This configuration also enables easymanagement of dimension accuracy.

As described above, in accordance with the first embodiment to which thepresent invention is applied, the vehicle 1 includes the vehicle body 10and the front wheel 2 that is disposed anterior to the vehicle body 10and is steerable about the steering axis Cs. The vehicle body 10includes the vehicle body frame 11 and the steering rotation unit 13that is supported on the vehicle body frame 11 and that rotates aboutthe steering axis Cs. The vehicle 1 further includes the variable traillength mechanism 30 that varies the trail length t of the front wheel 2.The variable trail length mechanism 30 includes the oscillation unit 41that supports the front forks 25L and 25R that are disposed to beoscillatable in the fore-aft direction and that support the front wheel2 and the electric motor 42 as a drive source for oscillating theoscillation unit 41. The electric motor 42 is supported on the vehiclebody 10. The electric motor 42, being supported on the vehicle body 10,is close to the steering axis Cs, so that steering inertia can bereduced.

Additionally, the electric motor 42, because being supported by thesteering rotation unit 13 of the vehicle body 10, is close to thesteering axis Cs. The steering inertia can thus be reduced.Additionally, because the steering rotation unit 13 rotates integrallywith the oscillation unit 41, the driving force of the electric motor 42that is supported by the steering rotation unit 13 can be transmitted,through a simple structure, to the oscillation unit 41 to therebyoscillate the oscillation unit 41.

The electric motor 42 is disposed, in a vehicle side elevational view,anterior to the steering rotation unit 13 and has the axis 42 c of therotary shaft 42 b thereof oriented in the vertical direction of thevehicle 1. Thus, the electric motor 42 can be compactly disposed and thesteering inertia can be reduced. It is noted that the axis 42 c isrequired only to be oriented vertically in the vehicle 1. For example,the axis 42 c may be oriented substantially perpendicularly.Alternatively, the axis 42 c may be oriented vertically in an inclinedposture in the vehicle side elevational view as depicted in FIG. 10.

The variable trail length mechanism 30 further includes the ball screwmechanism 43 that translates rotation of the electric motor 42 to linearmotion to thereby oscillate the oscillation unit 41. The ball screwmechanism 43 is disposed such that the threaded shaft 51 thereof has anaxis extending in parallel with the axis 42 c of the electric motor 42,so that the electric motor 42 and the ball screw mechanism 43 can becompactly disposed. The steering inertia can thus be reduced.

The variable trail length mechanism 30 further includes the speedreducer 45 that transmits rotation of the electric motor 42 to the ballscrew mechanism 43 with reduced speed and the lock mechanism 46 thatrestricts rotation of the electric motor 42 and that is disposedupstream of the speed reducer 45 in the path along which the rotation ofthe electric motor 42 is transmitted. The foregoing arrangement resultsin the rotation transmitted from the oscillation unit 41 side to theelectric motor 42 via the ball screw mechanism 43 and the speed reducer45 building up speed, so that torque transmitted from the oscillationunit 41 side to the electric motor 42 via the speed reducer 45 is small.Thus, the lock mechanism 46 disposed upstream of the speed reducer 45,even with a compact configuration, can still restrict rotation of theelectric motor 42 and operation of the variable trail length mechanism30 can be easily restricted.

Additionally, the lock mechanism 46, because having an axis coaxial withthe axis 42 c of the electric motor 42, can be built compactly.

The variable trail length mechanism 30 further includes the linkagemechanism 47 that connects the ball screw mechanism 43 with theoscillation unit 41 and the steering rotation unit 13. The steeringrotation unit 13 includes the steering shaft 32 journaled by the headpipe 17 of the vehicle body frame 11, the top bridge 33 fixed to theupper end portion of the steering shaft 32, and the bottom member 34fixed to the lower end portion of the steering shaft 32. The oscillationunit 41 is oscillatably supported via the oscillation shaft 48 disposedin the top bridge 33 and connected to the bottom member 34 via thelinkage mechanism 47. This arrangement allows the oscillation unit 41that is oscillatable about the oscillation shaft 48 of the top bridge 33to be oscillated via the linkage mechanism 47 connected with the bottommember 34. Thus, the oscillation unit 41 can be oscillated by a compactstructure to thereby change the trail length t.

Additionally, the oscillation unit 41 includes the bottom bridge 49 thatconnects the left and right front forks 25L and 25R and the linkagemechanism 47 is connected with the bottom bridge 49. This arrangementenables a compact structure to connect the linkage mechanism 47 with theoscillation unit 41 using the bottom bridge 49 that increases stiffnessof the front forks 25L and 25R.

Additionally, the bracket 36 that connects the top bridge 33 of thesteering rotation unit 13 with the bottom member 34 is disposed anteriorto the head pipe 17. The electric motor 42 is supported on the vehiclebody 10 via the bracket 36. Specifically, the bracket 36, becauseconnecting the top bridge 33 with the bottom member 34 at a positionanterior to the head pipe 17, is close to the steering axis Cs. Theelectric motor 42 thus can be disposed close to the steering axis Cs, sothat the steering inertia can be reduced.

Additionally, in accordance with the first embodiment, the vehicle 1includes the vehicle body 10, the front wheel 2 that is disposedanterior to the vehicle body 10 and is steerable about the steering axisCs, and the front forks 25L and 25R that support the front wheel 2. Thevehicle body 10 includes the vehicle body frame 11 and the steeringrotation unit 13 that is supported on the vehicle body frame 11 and thatrotates about the steering axis Cs. The vehicle 1 further includes thevariable trail length mechanism 30 that varies the trail length t of thefront wheel 2. The variable trail length mechanism 30 includes theoscillation shaft 48 that extends in the vehicle width direction andconnects the front forks 25L and 25R oscillatably with the steeringrotation unit 13. The oscillation shaft 48 is disposed, in the vehicleside elevational view, to be aligned with the fork axis 25 a of thefront forks 25L and 25R. Thus, because the front forks 25L and 25Roscillate about the oscillation shaft 48 disposed to be aligned with thefork axis 25 a, the inertia weight can be reduced when the trail lengtht is varied by oscillating the front forks 25L and 25R. Thus, the traillength t can be easily varied using the variable trail length mechanism30.

The oscillation shaft 48 is disposed at the upper end portions of thefront forks 25L and 25R and thus can be compactly disposed through aneffective use of a space at the upper end portions of the front forks25L and 25R. Additionally, the foregoing arrangement eliminates the needfor a space superior to the oscillation shaft 48, in which the frontforks 25L and 25R can be oscillated. This enhances a degree of freedomin disposing parts.

The front forks 25L and 25R are provided with the fork caps 25 d thatclose the upper surfaces of the front forks 25L and 25R and theoscillation shaft 48 is disposed in the fork caps 25 d. Thus, theoscillation shaft 48 can be provided using a simple structure that usesthe fork caps 25 d.

The steering rotation unit 13 includes the steering shaft 32 journaledby the head pipe 17 of the vehicle body frame 11, the top bridge 33fixed to the upper end portion of the steering shaft 32, and the bottommember 34 fixed to the lower end portion of the steering shaft 32. Thevariable trail length mechanism 30 includes the electric motor 42 andthe linkage mechanism 47 that connects the front forks 25L and 25R withthe bottom member 34 and that oscillates the front forks 25L and 25Rusing the driving force of the electric motor 42. The oscillation shaft48 is supported by the top bridge 33. This arrangement allows the frontforks 25L and 25R that are supported by the oscillation shaft 48 of thetop bridge 33 to be oscillated via the linkage mechanism 47 connectedwith the bottom member 34. Thus, the trail length t can be changed byoscillating the front forks 25L and 25R using a compact structure.

Additionally, the front forks 25L and 25R are an electronic controlsuspension capable of changing an axial length thereof and the vehicle 1includes the control apparatus 83 that drives the electronic controlsuspension so as to minimize changes in the vehicle height correspondingto the change in the vehicle height by the operation of the variabletrail length mechanism 30. Thus, the change in vehicle height can beminimized even when the trail length t is changed by the variable traillength mechanism 30. In addition, when the vehicle 1 is stationary, thevehicle height may be lowered using the electronic control suspension tothereby improve a property with which the operator (rider) can put bothfeet on the ground.

Additionally, in accordance with the first embodiment, the vehicle 1includes the vehicle body 10 and the front wheel 2 that is disposedanterior to the vehicle body 10 and is steerable about the steering axisCs. The vehicle body 10 includes the vehicle body frame 11 and thesteering rotation unit 13 that is supported on the vehicle body frame 11and that rotates about the steering axis Cs. The vehicle 1 furtherincludes the variable trail length mechanism 30 that varies the traillength t of the front wheel 2. The variable trail length mechanism 30includes the oscillation unit 41 that is connected with the steeringrotation unit 13 so as to be oscillatable in the fore-aft direction andthat supports the front wheel 2 and the torsion reduction portion 102that reduces torsion of the oscillation unit 41 in the vehicle widthdirection through the oscillation unit 41 combined with the steeringrotation unit 13 under the condition in which the trail length t ischanged such that the front wheel 2 is disposed at a rearmost position.The foregoing arrangement allows the torsion of the oscillation unit 41in the vehicle width direction to be reduced through the oscillationunit 41 combined with the steering rotation unit 13 under the ordinarytraveling state in which the vehicle 1 travels with the trail length tchanged such that the front wheel 2 is disposed at the rearmostposition, so that the oscillation unit 41 can be prevented from beingdeformed in the vehicle width direction during traveling. Thus,stiffness of the front wheel 2 surrounding structure during the ordinarytraveling state can be enhanced.

Additionally, the torsion reduction portion 102 includes the fittedportion 90 disposed in the steering rotation unit 13 and the fittingportion 100 that is disposed in the oscillation unit 41 and that can befitted in the fitted portion 90. The fitting portion 100 may be fittedin the fitted portion 90 under the condition in which the trail length tis changed such that the front wheel 2 is disposed at the rearmostposition. Through the foregoing arrangement, during the ordinarytraveling state in which the vehicle 1 travels with the trail length tchanged such that the front wheel 2 is disposed at the rearmostposition, the fitting portion 100 of the oscillation unit 41 fits in thefitted portion 90 of the steering rotation unit 13 to thereby preventthe oscillation unit 41 from being deformed in the vehicle widthdirection during traveling. Thus, the stiffness of the front wheel 2surrounding structure during the ordinary traveling state can beenhanced.

Additionally, the oscillation unit 41 includes the bottom bridge 49 thatconnects the pair of left and right front forks 25L and 25R that supportthe front wheel 2 and the fitting portion 100 is disposed in the bottombridge 49. This arrangement permits use of a simple structure of thebottom bridge 49 that enhances stiffness of the front forks 25L and 25Rin disposing the fitting portion 100.

The steering rotation unit 13 includes the steering shaft 32 journaledby the head pipe 17 of the vehicle body frame 11, the top bridge 33fixed to the upper end portion of the steering shaft 32, and the bottommember 34 fixed to the lower end portion of the steering shaft 32. Thefitted portion 90 is disposed in the bottom member 34. This arrangementpermits use of a simple structure of the bottom member 34 of thesteering rotation unit 13 in disposing the fitted portion 90.Additionally, because the bottom member 34 rotates integrally with theoscillation unit 41, the fitting portion 100 can be fitted into thefitted portion 90 with a simple structure.

The fitting portion 100, because having the left and right protrusionlateral surfaces 100 c, 100 c that abut on the fitted portion 90 in thevehicle width direction, can effectively reduce deformation of theoscillation unit 41 in the vehicle width direction.

The fitting portion 100 and the fitted portion 90 are configured as aset of a protrusion and a recess. The protrusion lateral surfaces 100 c,100 c that assume the lateral surfaces in the vehicle width direction ofthe protrusion are inclined such that the protrusion has the taperingleading end 100 d. Thus, the inclination of the protrusion lateralsurfaces 100 c, 100 c serve as a guide for the protrusion to fit in thefitted portion 90 as the recess, so that the protrusion can be easilyfitted in the recess. Additionally, the fitting portion 100 is theprotrusion protruding to the rear and the fitted portion 90 is therecess in which the protrusion fits. Thus, under a condition in whichthe trail length t has been changed such that the front wheel 2 isdisposed at the rearmost position, the fitting portion 100 can be fittedin the fitted portion 90.

Second Embodiment

A second embodiment to which the present invention is applied will bedescribed below with reference to FIG. 13. In the second embodiment,like or identical parts described in the first embodiment are denoted bylike or identical reference symbols and descriptions therefor will beomitted.

The first embodiment has been described for the structure in which theelectric motor 42, the ball screw mechanism 43, and the like oscillatethe front forks 25L and 25R to thereby change the trail length t. Thesecond embodiment will be described for another configuration foroscillating the front forks 25L and 25R.

FIG. 13 is a left side elevational view depicting schematically a frontportion of a vehicle 1 according to the second embodiment.

A vehicle body 210 includes a vehicle body frame 11 and a steeringrotation unit 213.

The steering rotation unit 213 is rotatably supported by a head pipe 17.The steering rotation unit 213 includes a top bridge 233, a steeringshaft 32 (FIG. 9), and a bottom member 234. The steering rotation unit213 rotates integrally about a steering axis Cs that is aligned with anaxis of the steering shaft 32.

A bracket 236 that vertically connects the top bridge 233 with thebottom member 234 at a position anterior to the head pipe 17 is mountedon the steering rotation unit 213.

A variable trail length mechanism 230 includes an oscillation unit 241,a hydraulic actuator 242, and a link 247. The oscillation unit 241 isconnected with the steering rotation unit 213 oscillatably in thefore-aft direction. The hydraulic actuator 242 serves as a drive sourcefor oscillating the oscillation unit 241. The link 247 connects thebottom member 234 with the front forks 25L and 25R.

The front forks 25L and 25R have upper portions supported by theoscillation unit 241 and extend downwardly.

The oscillation unit 241 includes an upper guide portion 220 and a lowerguide portion 221. The upper guide portion 220 is disposed at the upperend portions of the front forks 25L and 25R. The lower guide portion 221is disposed on the front forks 25L and 25R at a position inferior to theupper guide portion 220.

The upper guide portion 220 includes an upper roller member 220 a and anupper guide rail 220 b. The upper roller member 220 a is disposed onrear surfaces of the front forks 25L and 25R. The upper guide rail 220 bis disposed on a front surface of the bracket 236. The upper guide rail220 b includes a rail portion 220 c that extends vertically. The railportion 220 c extends, in a side elevational view, from an upper enddownwardly toward the front and then extends downwardly andsubstantially vertically before extending downwardly toward the front upto a lower end.

The upper roller member 220 a includes a pair of rollers that clamp therail portion 220 c from the front and rear. The upper roller member 220a moves in the vertical direction and the fore-aft direction along therail portion 220 c.

The lower guide portion 221 includes a lower roller member 221 a and alower guide rail 221 b. The lower roller member 221 a is disposed on therear surfaces of the front forks 25L and 25R. The lower guide rail 221 bis disposed on a front surface of a lower portion of the steeringrotation unit 213. The lower guide rail 221 b includes a rail portion221 c that extends vertically. The rail portion 221 c extends, in theside elevational view, from an upper end downwardly toward the front andthen extends substantially horizontally before extending againdownwardly toward the front up to a lower end.

The lower roller member 221 a includes a pair of rollers that clamp therail portion 221 c from the front and rear. The lower roller member 221a moves in the vertical direction and the fore-aft direction along therail portion 221 c.

The hydraulic actuator 242 is supported by a stay 213 a that extendstoward the front from an upper portion of the bracket 236 of thesteering rotation unit 213. The hydraulic actuator 242 is disposedsuperior to the front forks 25L and 25R.

The hydraulic actuator 242 includes an actuating portion 242 a. Theactuating portion 242 a extends downwardly and is connected with frontsurfaces of the upper end portions of the front forks 25L and 25R. Theactuating portion 242 a makes a vertical stroke motion.

The hydraulic actuator 242 receives hydraulic pressure supplied from,for example, a hydraulic generator in the vehicle body 210. Operation ofthe hydraulic actuator 242 is controlled by a control apparatus 83.

When the actuating portion 242 a of the hydraulic actuator 242 operates,the upper roller member 220 a and the lower roller member 221 a movealong the rail portion 220 c and the rail portion 221 c, respectively,so that the front forks 25L and 25R oscillate in the fore-aft directionwith a position near the upper guide portion 220 and the lower guideportion 221 as a base point. This changes the trail length t and movesmounting portions of the front forks 25L and 25R downward, so that achange in vehicle height can be minimized even with the trail length tchanged. This eliminates the electronic control suspension as thatdescribed in the first embodiment.

In the second embodiment, the hydraulic actuator 242 is supported by thesteering rotation unit 213 of the vehicle body 210. This arrangementresults in the hydraulic actuator 242 being close to the steering axisCs, so that steering inertia can be reduced.

Third Embodiment

A third embodiment to which the present invention is applied will bedescribed below with reference to FIG. 14. In the third embodiment, likeor identical parts described in the first embodiment are denoted by likeor identical reference symbols and descriptions therefor will beomitted.

The first embodiment has been described for the arrangement in which thefront forks 25L and 25R oscillate about the oscillation shaft 48disposed at the upper end portions of the front forks 25L and 25R. Thethird embodiment will be described for a configuration in which anoscillation shaft 348 is disposed inferior to the upper end portions ofthe front forks 25L and 25R.

FIG. 14 is a left side elevational view depicting a front portion of avehicle 1 according to a third embodiment.

A vehicle body 310 includes a vehicle body frame 11 and a steeringrotation unit 313.

The steering rotation unit 313 is rotatably supported by a head pipe 17.The steering rotation unit 313 includes a top bridge 333, a steeringshaft 32 (FIG. 9), and a bottom member 334. The steering rotation unit313 rotates integrally about a steering axis Cs that is aligned with anaxis of the steering shaft 32.

The steering rotation unit 313 includes a bracket 336 that verticallyconnects the top bridge 333 with the bottom member 334 at a positionanterior to the head pipe 17.

The steering rotation unit 313 includes an oscillation shaft supportportion 334 a that extends toward the front from the bottom member 334.

A variable trail length mechanism 330 includes an oscillation unit 341,an electric motor 42, a ball screw mechanism 43, a speed reducer 45, alock mechanism 46, and a linkage mechanism 347. The oscillation unit 341is connected with the steering rotation unit 313 oscillatably in thefore-aft direction. The linkage mechanism 347 connects the ball screwmechanism 43 with the oscillation unit 341 and the steering rotationunit 313.

In the third embodiment, the electric motor 42, the ball screw mechanism43, the speed reducer 45, and the lock mechanism 46 are disposed insubstantially reverse order vertically relative to the configuration ofthe first embodiment.

The ball screw mechanism 43 is mounted on the bracket 336 via supportpieces 357, 357. Specifically, the electric motor 42 is supported by thesteering rotation unit 313 of the vehicle body 310 via, for example, thebracket 336.

The oscillation unit 341 includes the oscillation shaft 348 and a linkconnecting portion 350. The oscillation shaft 348 extends in the vehiclewidth direction and connects the front forks 25L and 25R oscillatablywith the steering rotation unit 313. The link connecting portion 350 isdisposed at the upper end portions of the front forks 25L and 25R andconnected with the linkage mechanism 347.

The oscillation shaft 348 is supported at a front end portion of theoscillation shaft support portion 334 a of the bottom member 334.

The linkage mechanism 347 includes a first link 361, a second link 362,and a third link 63. The first link 361 connects the top bridge 333 withthe ball screw mechanism 43. The second link 362 connects the first link361 with the link connecting portion 350 of the oscillation unit 341.The third link 63 connects the first link 361 with a moving portion 52 bof the ball screw mechanism 43.

The front forks 25L and 25R are connected with each other in the vehiclewidth direction by a bottom bridge 349 disposed anterior to the bottommember 334.

The bottom member 334 includes an oscillation shaft connecting portion349 a disposed at a position overlapping a fork axis 25 a in the sideelevational view. The oscillation shaft 348 is passed through theoscillation shaft connecting portion 349 a of the bottom member 334 tothereby be connected with the bottom member 334.

When the electric motor 42 is driven, the oscillation unit 341oscillates via the linkage mechanism 347 and the link connecting portion350 oscillates in the fore-aft direction about the oscillation shaft348. This causes the front forks 25L and 25R to oscillate in thefore-aft direction about the oscillation shaft 348 that is disposed tooverlap the fork axis 25 a in the side elevational view, so that a traillength t is changed.

In the third embodiment, the steering rotation unit 313 includes thesteering shaft 32 (FIG. 9) journaled by the head pipe 17 of the vehiclebody frame 11, the top bridge 333 fixed at the upper end portion of thesteering shaft 32, and the bottom member 334 fixed at the lower endportion of the steering shaft 32, and the oscillation shaft 348 isdisposed at a position that overlaps the fork axis 25 a and that iscloser to the bottom member 334 than to the top bridge 333 in the sideelevational view. This arrangement causes the front forks 25L and 25R tooscillate about the oscillation shaft 348 disposed at the positioncloser to the bottom member 334, so that a change in vehicle height whenthe trail length t is changed by the variable trail length mechanism 330can be minimized.

Additionally, the bottom bridge 349 connects the pair of left and rightfront forks 25L and 25R each other and the oscillation shaft 348 isdisposed on the bottom bridge 349 at the position overlapping the forkaxis 25 a in the side elevational view. This arrangement enables theoscillation shaft 348 to be disposed in a simple structure using thebottom bridge 349 that improves stiffness of the front forks 25L and25R.

In addition, the oscillation unit 341 includes a fitting portion 300that protrudes to the front from the link connecting portion 350.

The steering rotation unit 313 includes a forward extension portion 333a that extends forward relative to the front forks 25L and 25R. Theforward extension portion 333 a includes a fitted portion 390 disposedanterior to the fitting portion 300.

The fitting portion 300 has a protrusion having, for example, aforwardly protruding shape identical to the shape of the fitting portion100 in the first embodiment. The fitted portion 390 is a recess having ashape identical to the shape of the fitted portion 90 in the firstembodiment.

When the “ordinary state” is set as a result of the upper portions ofthe front forks 25L and 25R oscillating forward from the “trail lengthchanged state” of FIG. 14 about the oscillation shaft 348, the fittingportion 300 fits into the fitted portion 390. This enhances stiffness ofthe structure surrounding a front wheel 2 in the “ordinary state.”

Fourth Embodiment

A fourth embodiment to which the present invention is applied will bedescribed below with reference to FIG. 15. In the fourth embodiment,like or identical parts described in the first embodiment are denoted bylike or identical reference symbols and descriptions therefor will beomitted.

The first embodiment has been described for the arrangement in which thefront forks 25L and 25R oscillate about the oscillation shaft 48disposed at the upper end portions of the front forks 25L and 25R. Thefourth embodiment will be described for a configuration in which anoscillation shaft 348 is disposed inferior to the upper end portions ofthe front forks 25L and 25R and the front forks 25L and 25R areoscillated using a drive source different from the electric motor 42.

FIG. 15 is a left side elevational view depicting schematically a frontportion of a vehicle 1 according to the fourth embodiment.

A vehicle body 410 includes a vehicle body frame 11 and a steeringrotation unit 413.

The steering rotation unit 413 is rotatably supported by a head pipe 17.The steering rotation unit 413 includes a top bridge 433, a steeringshaft 32 (FIG. 9), and a bottom member 434. The steering rotation unit413 rotates integrally about a steering axis Cs that is aligned with anaxis of the steering shaft 32.

The steering rotation unit 413 includes a bracket 436 that verticallyconnects the top bridge 433 with the bottom member 434 at a positionanterior to the head pipe 17.

A variable trail length mechanism 430 includes a drive source 442, anoscillation unit 441, an oscillation shaft 448, and a link 447. Theoscillation unit 441 is connected with the front forks 25L and 25R andis oscillated in the fore-aft direction by a driving force of the drivesource 442. The oscillation shaft 448 extends in the vehicle widthdirection and connects the front forks 25L and 25R oscillatably with thesteering rotation unit 413. The link 447 connects upper end portions ofthe front forks 25L and 25R with the steering rotation unit 413.

The drive source 442 is a screw mechanism driven by a motor anddisplaced linearly in the vertical direction. The drive source 442 isfixed to the bracket 436.

The oscillation unit 441 includes a roller member 420 and a guide rail421. The roller member 420 is disposed posterior to the front forks 25Land 25R. The guide rail 421 is moved in the vertical direction by thedrive source 442.

The oscillation unit 441 and the drive source 442 are disposed at aposition superior to the bottom member 434 and the oscillation shaft 448and posterior to the upper portions of the front forks 25L and 25R. Theoscillation shaft 448 is disposed, in the vehicle side elevational view,at a position overlapping an fork axis 25 a.

The guide rail 421 extends, in the side elevational view, from an upperend downwardly toward the front and then extends substantiallyhorizontally before extending again downwardly toward the front up to alower end.

The roller member 420 includes a pair of rollers that clamp the guiderail 421 from the front and rear. The guide rail 421 moves in thevertical direction under a condition of being clamped between the tworollers of the roller member 420.

When the drive source 442 is energized by a control apparatus 83 (FIG.11), the guide rail 421 moves vertically and the roller member 420follows the shape of the guide rail 421 to thereby oscillate in thefore-aft direction. This causes the front forks 25L and 25R to oscillatein the fore-aft direction integrally with the guide rail 421 about theoscillation shaft 448, so that a trail length t is changed.

FIG. 16 is a side elevational view depicting a modification of thefourth embodiment.

As depicted in FIG. 16, a pneumatic actuator 412 may be provided as adrive source, in place of the drive source 442 and the oscillation unit441 depicted in FIG. 15.

The actuator 412 extends in the fore-aft direction to thereby connectthe upper portions of the front forks 25L and 25R with the steeringrotation unit 413. A pneumatic pressure source 415 disposed in thevehicle body 410 supplies the actuator 412 with air pressure.

The actuator 412 includes a cylinder 412 a and a piston 412 b disposedin the cylinder 412 a. The piston 412 b separates the cylinder 412 ainto an anterior chamber 412 c and a posterior chamber 412 d.

The pneumatic pressure source 415 is connected with the anterior chamber412 c by a first air passage 416 and with the posterior chamber 412 d bya second air passage 417. The first air passage 416 and the second airpassage 417 are provided with a valve 416 a and a valve 417 a,respectively. The valve 416 a and the valve 417 a are each opened andclosed by the control apparatus 83.

When air pressure is supplied to the posterior chamber 412 d, the piston412 b moves forward and an actuating portion of the piston 412 b pushesthe front forks 25L and 25R forward. This causes the upper portions ofthe front forks 25L and 25R to oscillate in the forward direction aboutthe oscillation shaft 448, thus setting the vehicle 1 in the “ordinarystate.”

When air pressure is supplied to the anterior chamber 412 c, the piston412 b moves backward and the actuating portion of the piston 412 b pullsthe front forks 25L and 25R forward. This causes the upper portions ofthe front forks 25L and 25R to oscillate in the backward direction aboutthe oscillation shaft 448, thus setting the vehicle 1 in the “traillength changed state.”

Fifth Embodiment

A fifth embodiment to which the present invention is applied will bedescribed below with reference to FIG. 17. In the fifth embodiment, likeor identical parts described in the first embodiment are denoted by likeor identical reference symbols and descriptions therefor will beomitted.

The first embodiment has been described for the arrangement in which thefitting portion 100 and the fitted portion 90 are each disposed at thecenter in the vehicle width. The fifth embodiment will be described foranother exemplary arrangement of the fitting portion and the fittedportion.

FIG. 17 is a cross-sectional view taken along line XII-XII in FIG. 6according to the fifth embodiment.

As depicted in FIG. 17, a possible arrangement may include a pluralityof protrusions and recesses arrayed in the vehicle width direction, eachpair of one protrusion and one recess constituting a pair of a fittingportion 100 and a fitted portion 90.

Alternatively, the fitting portion 100 may have a leading end 100 dformed into a flat surface extending in parallel with a rear surface 49b of a bottom bridge 49, to thereby be formed into a trapezoid. In thiscase, the fitted portion 90 may have a bottom portion 90 d formed into aflat surface to thereby be formed into a trapezoid.

Alternatively, the fitting portion 100 may be formed into a conicalshape that protrudes toward the rear so as to have a tapering leadingend. In this case, the fitted portion 90 is formed into a conicalrecess.

Alternatively, the fitted portion 90 in a bottom member 34 may be aprotrusion protruding to the front and the fitting portion 100 of thebottom bridge 49 may be a recess in which the protrusion fits.

Still alternatively, the fitting portion 100 may be configured as amember separate from the bottom bridge 49 and configured to be removablewith respect to the bottom bridge 49. In this case, the bottom bridge 49may be formed of metal and the fitting portion 100 may be formed of amaterial (e.g., resin) different from the material of the bottom bridge49.

Similarly, the fitted portion 90 may be configured as a member separatefrom the bottom member 34 and configured to be removable with respect tothe bottom member 34. In this case, the bottom member 34 may be formedof metal and the fitted portion 90 may be formed of a material (e.g.,resin) different from the material of the bottom member 34.

FIGS. 18 and 19 are each a schematic view depicting a variation ofshapes of the fitting portion 100 and the fitted portion 90. FIGS. 18and 19 are each a view in the axial direction of the steering shaft 32.

As depicted in FIG. 18, two fitting portions 100, 100 may be formed onboth lateral end portions of the rear surface 49 b of the bottom bridge49 and one fitted portion 90 may be formed in the front surface 34 a ofthe bottom member 34. In the example depicted in FIG. 18, the fittedportion 90 is formed to extend over a wide range between both endportions of the front surface 34 a in the vehicle width direction. Thefitting portions 100 are configured such that protrusion lateralsurfaces 100 c on the outside in the vehicle width direction of therespective fitting portions 100 fit in respective recess lateralsurfaces 90 c, 90 c of the fitted portion 90. Additionally, in theexample depicted in FIG. 18, under a condition in which the fittingportions 100, 100 fit in the fitted portion 90, a gap is formed betweeneach of the leading ends 100 d and the bottom portion 90 d and betweenthe rear surface 49 b and the front surface 34 a.

Reference is made to FIG. 19. An arrangement may be possible in whichthe front surface 34 a of the bottom member 34 may generally be definedas a fitting portion 150 as a forwardly protruding protrusion and afitted portion 160 as a recess in which the fitting portion 150 fits maybe formed in the rear surface 49 b of the bottom bridge 49.

The fitting portion 150 has protrusion lateral surfaces 150 c, 150 cthat are inclined so that the fitting portion 150 has a tapering leadingend 150 d.

The fitted portion 160 has recess lateral surfaces 160 c, 160 c in whichthe protrusion lateral surfaces 150 c, 150 c fit. Under a condition inwhich the fitting portion 150 fits in the fitted portion 160, a gap isformed between the leading end 150 d of the fitting portion 150 and abottom portion 160 d of the fitted portion 160.

While the present invention has been particularly described withreference to various embodiments, it will be understood that the firstto fifth embodiments are not intended to limit the present invention.

While the first to fifth embodiments have been described as applied to amotorcycle, the invention is applicable to not only the motorcycle, butalso three-wheel saddled vehicles having two front or rear wheels,four-or-more-wheel saddled vehicles, and scooter and related types ofsaddled vehicles.

DESCRIPTION OF REFERENCE SYMBOLS

-   1 Vehicle-   2 Front wheel-   10, 210, 310 Vehicle body-   11 Vehicle body frame-   13, 313, 413 Steering rotation unit-   17 Head pipe-   25L, 25R Front fork-   25 a Fork axis (front fork axis)-   25 d Fork cap-   30, 330, 430 Variable trail length mechanism-   32 Steering shaft-   33, 333, 433 Top bridge-   34, 334, 434 Bottom member-   42 Electric motor (drive source)-   47 Linkage mechanism-   48, 348, 448 Oscillation shaft-   83 Control apparatus-   349 Bottom bridg-   Cs Steering axis-   T Trail length

1. A vehicle including a vehicle body, a front wheel that is disposedanterior to the vehicle body and that is steerable about a steeringaxis, and a front fork that supports the front wheel, the vehicle bodyincluding a vehicle body frame and a steering rotation unit that issupported on the vehicle body frame and that rotates about the steeringaxis, the vehicle comprising: a variable trail length mechanism thatvaries a trail length of the front wheel, the variable trail lengthmechanism including an oscillation shaft that extends in a vehicle widthdirection to thereby connect the front fork oscillatably with thesteering rotation unit, wherein the oscillation shaft is disposed at aposition overlapping an axis of the front fork in a vehicle sideelevational view.
 2. The vehicle according to claim 1, wherein theoscillation shaft is disposed at an upper end portion of the front fork.3. The vehicle according to claim 2, wherein the front fork has a forkcap that closes an upper surface of the front fork, and the oscillationshaft is disposed in the fork cap.
 4. The vehicle according to any oneof claim 1, wherein the steering rotation unit includes a steering shaftjournaled by a head pipe of the vehicle body frame, a top bridge fixedto an upper end portion of the steering shaft, and a bottom member fixedto a lower end portion of the steering shaft, the variable trail lengthmechanism includes a drive source and a linkage mechanism that connectsthe front fork with the bottom member and that oscillates the front forkthrough a driving force of the drive source, and the oscillation shaftis supported by the top bridge.
 5. The vehicle according to claim 1,wherein the steering rotation unit includes a steering shaft journaledby a head pipe of the vehicle body frame, a top bridge fixed to an upperend portion of the steering shaft, and a bottom member fixed to a lowerend portion of the steering shaft, and the oscillation shaft is disposedat, in a side elevational view, a position overlapping the axis andcloser to the bottom member than to the top bridge.
 6. The vehicleaccording to claim 5, further comprising: a bottom bridge that connectsa left and right pair of the front forks, wherein the oscillation shaftis disposed in the bottom bridge at a position overlapping the axis in aside elevational view.
 7. The vehicle according to any one of claim 1,wherein the front fork constitutes an electronic control suspensioncapable of changing an axial length of the front fork, the vehiclefurther comprising: a control apparatus that drives the electroniccontrol suspension so as to minimize a change in a vehicle heightcorresponding to the change in the vehicle height by an operation of thevariable trail length mechanism.